Remote into a second computer on LAN

I have a Server 2012 machine that I regularly remote into using RDP. I also have a static IP address and an attached domain.

I have a second machine on my network that I would like to remote into as well. I have tried to alter the port (from 3389 to 3390) which works in some networks, but one of the networks I am on regularly does not have 3390 outgoing open.

My question...is there a way to use a subdomain or the firewall (seperate device) or server 2012 to route my 3389 request to the other machine?